Cubic chromium trifluoride and its use for halogenated hydrocarbon processing

ABSTRACT

This invention provides a crystalline chromium fluoride having a cubic crystal structure (i.e., chromium trifluoride having an X-ray diffraction powder pattern as shown in Table I); and a catalytic composition comprising cubic chromium trifluoride. This invention also provides a process for changing the fluorine content of halogenated hydrocarbons containing from one to six carbon atoms, in the presence of a chromium-containing catalyst. The process is characterized by the chromium-containing catalyst comprising cubic chromium trifluoride.

This application claims the priority benefit of U.S. ProvisionalApplication Ser. No. 60/056,792, filed Aug. 25, 1997.

FIELD OF THE INVENTION

This invention relates to chromium-containing catalysts and their use inthe processing of halogenated hydrocarbons.

BACKGROUND

A number of chlorine-containing halocarbons are considered to bedetrimental toward the Earth's ozone layer. There is a world-wide effortto develop materials having lower ozone depletion potentials that canserve as effective replacements. For example, the hydrofluorocarbon,1,1,1,2-tetrafluoroethane (HFC-134a) is being used as a replacement fordichlorodifluoromethane (CFC-12) in refrigeration systems. There is aneed for manufacturing processes that provide fluorocarbons that containless chlorine or no chlorine.

Numerous processes have been developed for changing the fluorine contentof halogenated hydrocarbons. Various catalysts have been proposed foruse in facilitating processes such as fluorination. See, e.g., L. E.Manzer et al., Adv. Catal. (39) pp. 329-350 (1993).

Chromia catalysts, which include crystalline Cr₂ O₃, amorphous phasesand mixtures, have been widely used for halogenated hydrocarbonprocessing. Typically, the activity of these chromia catalysts decreasewith time during their use in hydrofluorination processes. WO 94/06558discloses that a major cause of this deactivation is the conversion ofchromia to chromium trifluoride. CrF₃ has been reported to formrhombohedral crystals (see e.g., Ullman's Encyclopedia of IndustrialChemistry, Fifth Ed., Vol. A7, p. 83). There is an ongoing interest indeveloping efficient catalysts for changing the fluorine content ofhalogenated hydrocarbons.

SUMMARY OF THE INVENTION

This invention provides a crystalline chromium fluoride having a cubiccrystal structure (i.e., chromium trifluoride having an X-raydiffraction powder pattern as shown in Table I); and a catalyticcomposition comprising cubic chromium trifluoride. This invention alsoprovides a process for changing the fluorine content of halogenatedhydrocarbons containing from one to six carbon atoms, in the presence ofa chromium-containing catalyst. The process is characterized by thechromium-containing catalyst comprising cubic chromium trifluoride.

DETAILED DESCRIPTION

This invention involves cubic chromium trifluoride, a composition havingan X-ray diffraction powder pattern as shown in Table I, as follows:

                  TABLE I                                                         ______________________________________                                        Powder X-ray diffraction Data for Cubic-CrF.sub.3                               d spacing (Å)                                                                           Relative intensity.sup.(a)                                                                 H      K   L                                     ______________________________________                                        5.8888      VS.sup.(b)   1        1   1                                         3.0674 S.sup.(c) 3 1 1                                                        2.9423 M.sup.(d) 2 2 2                                                        2.0818 W.sup.(e) 4 2 2                                                        1.9547 W.sup.(e) 5 1 1                                                        1.7991 M.sup.(d) 4 4 0                                                      ______________________________________                                         .sup.(a) as recorded at room temperature using a conventional                 diffractometer such as SCINTAG (PAD IV) diffractometer with copper kalpha     radiation                                                                     .sup.(b) VS means very strong (e.g., a relative intensity of about 100)       .sup.(c) S means strong (e.g., a relative intensity of about 46)              .sup.(d) M means moderate (e.g., a relative intensity of about 33 and         about 14 for d spacing of 2.9423 and 1.7991, respectively)                    .sup.(e) W means weak (e.g., a relative intensity of about 7 and about 4      for d spacing of 2.0818 and 1.9547, respectively)                        

Cubic chromium trifluoride may be prepared from CrF₃ •XH₂ O, where X is3 to 9, preferably 4, by heating in air or an inert atmosphere (e.g.,nitrogen or argon) at 350° C. to 400° C. for 3 to 12 hours, preferably 3to 6 hours. The color of cubic chromium trifluoride is dark green.

Cubic chromium trifluoride is useful by itself and together with otherchromium compounds, as a catalytic material. Of note are catalystcompositions comprising chromium wherein at least 10% of the chromium isin the form of cubic chromium trifluoride, particularly catalystcompositions wherein at least 25% of the chromium is in the form ofcubic chromium trifluoride, and especially catalyst compositions whereinat least 60% of the chromium is in the form of cubic chromiumtrifluoride. The chromium, including the cubic chromium trifluoride canbe supported on and/or physically mixed with materials such as carbon,aluminum fluoride, fluorided alumina, lanthanum fluoride, magnesiumfluoride, calcium fluoride, zinc fluoride and the like. Preferred arecombinations including cubic chromium trifluoride in combination withmagnesium fluoride and/or zinc fluoride. Chromium trifluoride catalystwhich consists essentially of cubic chromium trifluoride can also beprepared and used in accordance with this invention.

The cubic chromium trifluoride-containing catalyst may be of variousphysical shapes, including for example, pellets, powders and granules.

Included in this invention is a process for increasing the fluorinecontent of a saturated or olefinic halogenated hydrocarbon startingmaterial of the formula C_(n) H_(a) Cl_(b) F_(c), wherein n is aninteger from 1 to 6, a is an integer from 0 to to 12, b is an integerfrom 0 to 13 and c is an integer from 0 to 13, provided that b is atleast 1 when the compound is saturated, by reacting said compound withHF in the vapor phase; and a process for the disproportionation of acompound having the formula C_(p) H_(g) F_(h) Cl, where p is an integerfrom 1 to 2, g is an integer from 1 to 3 and h is an integer from 1 to4. These processes are respectively characterized by reacting the C_(n)H_(a) Cl_(b) F_(c) compound with HF and conducting thedisproportionation of the C_(p) H_(g) F_(h) Cl compound, in the presenceof a catalyst comprising cubic chromium trifluoride.

The vapor phase contact of the cubic chromium trifluoride-containingcatalyst with the HF and the saturated or olefinic halogenatedhydrocarbons of the formula C_(n) H_(a) Cl_(b) F_(c), wherein n is aninteger from 1 to 6, a is an integer from 0 to to 12, b is an integerfrom 0 to 13 and c is an integer from 0 to 13, is typically conducted atfrom about 150° C. to 500° C. For saturated compounds the contact ispreferably from about 175° C. to 400° C., more preferably at from about200° C. to about 350° C. The contact time is typically from about 1 toabout 120 seconds (e.g., from about 5 to about 60 seconds). The amountof HF ordinarily should be at least a stoichiometric amount. Typically,the molar ratio of HF to the said compounds of the formula C_(n) H_(a)Cl_(b) F_(c) can range from about 0.5:1 to about 100:1, preferably about2:1 to 50:1, and more preferably from about 3:1 to 10:1. In general,with a given catalyst composition, the higher the temperature and thelonger the contact time, the greater is the conversion to fluorinatedproducts. The above variables can be balanced, one against the other, sothat the formation of higher fluorine substituted products is maximized.

Examples of olefinic compounds which may be reacted with HF in thepresence of the catalyst of this invention include CHCl═CCl₂, CCl₂═CCl₂, CCl₂ ═CH₂, CCl₂ ═CF₂, CHF═CF₂, CF₂ ═CH₂, CF₂ ═CFCl, CCl₂═CClCCl₃, CF₃ CCl═CF₂, CF₃ CH═CF₂, CF₃ CF═CHF and CCl₃ CCl═CClCCl₃. Ofnote is a catalytic process for producing 2-chloro-1,1,1-trifluoroethane (HCFC-133a) by the fluorination of a trihaloetheneof the formula CX₂ ═CHCl wherein each X is chlorine or fluorine.Starting materials include trichloroethene, 1,2-dichlorofluoroethene and1-chloro-2,2-difluoroethene. Trichloroethene is preferred. HCFC-133a isproduced by reacting the above unsaturated compounds with HF in thevapor phase in the presence of the catalyst of this invention. Thereaction of the above trihaloethenes with HF in the presence of thecatalyst of the instant invention is preferably conducted at about 150°C. to 350° C., more preferably about 175° C. to 250° C. Oxygen may beco-fed, if desired.

Also of note is a catalytic process for producing2,2-dichloro-1,1,1-trifluoroethane (i.e., CHCl₂ CF₃ or HCFC-123),1,1,1,2-tetrafluorochloroethane i.e., CHClFCF₃ or HCFC-124) andpentafluoroethane (i.e., CHF₂ CF₃ or HFC-125) by the fluorination of atetrahaloethene of the formula C₂ Cl_(4-x) F_(x), wherein x equals 0 to3 in the presence of the chromium trifluoride catalyst of thisinvention. Starting materials include CCl₂ ═CCl₂, CClF═CCl₂, CClF═CClF,CF₂ ═CCl₂ and CF₂ ═CClF. Tetrachloroethene is preferred. HCFC-123,HCFC-124 and/or HFC-125 are produced by reacting the above unsaturatedcompounds with HF in the vapor phase in the presence of the catalyst ofthis invention.

Examples of saturated compounds which may be reacted with HF in thepresence of the catalyst of this invention include CH₂ Cl₂, CHCl₃, C₂Cl₆, C₂ Cl₅ F, C₂ Cl₄ F₂, C₂ Cl₃ F₃, C₂ Cl₂ F₄, C₂ ClF₅, C₂ HCl₅, C₂HCl₄ F, C₂ HCl₃ F₂, C₂ HCl₂ F₃, C₂ HClF₄, C₃ HCl₇, C₃ HCl₆ F, C₃ HCl₅F₂, C₃ HCl₄ F₃, C₃ HCl₃ F₄, C₃ HCl₂ F₅, C₃ H₂ Cl₅ F, C₃ H₂ Cl₄ F₂, C₃ H₂Cl₃ F₃, C₃ H₂ Cl₂ F₄, C₃ H₂ ClF₅ and C₃ H₂ Cl₆ (e.g., CCl₃ CH₂ CCl₃).Mixtures of saturated compounds may also be used (e.g., a mixture of CH₂Cl₂ and CCl₃ CF₃ ; or a mixture of CCl₂ FCClF₂ and CCl₃ CF₃). Of noteare catalytic processes for reacting1,1,1-trichloro-2,2,2-trifluoroethane (i.e., CCl₃ CF₃ or CFC-113a), orreacting dichloromethane, with HF, in the vapor phase in the presenceofthe catalyst ofthis invention. For the reaction of CFC-113a with HF toyield CCl₂ FCF₃ (CFC-114a), the HF:CCl₃ CF₃ ratio can vary widely. TheHF:CFC-113a molar ratio should be at least 0.5:1, but is preferablywithin the range of from about 2:1 to about 10:1.

For the reaction of dichloromethane to yield difluoromethane (i.e., CH₂F₂ or HFC-32), the molar ratio of HF to CH₂ Cl₂ preferred ranges arefrom about 1:1 to about 10:1. The reaction temperature normally rangesfrom about 180° C. to about 375° C. (e.g., from about 200° C. to about350° C.).

For the reaction of mixtures of CH₂ Cl₂ and CCl₃ CF₃ to yield mixturesof CH₂ F₂ and CCl₂ FCF₃, the molar ratio of HF added to the total amountof CH₂ Cl₂ and CCl₃ CF₃ starting material typically ranges from about0.5:1 to about 10:1, and is preferably from about 1:1 to about 8:1.Typically, the molar ratio of CH₂ Cl₂ to CCl₃ CF₃ in mixtures rangesfrom about 1:9 to about 9:1.

For the reaction of mixtures of CCl₂ FCClF₂ and CCl₃ CF₃ to yieldmixtures of CClF₂ CClF₂ and CCl₂ FCF₃, the molar ratio of HF added tothe total amount of CCl₂ FCClF₂ and CCl₃ CF₃ starting material typicallyranges from about 1:1 to about 10:1, and is preferably from about 1:1 toabout 5:1. Typically, the molar ratio of CCl₂ FCClF₂ to CCl₃ CF₃ inmixtures ranges from about 1:99 to about 9:1. The reaction of C₂ Cl₃ F₃with HF in the presence of the catalyst of this invention can be used toobtain mixtures enriched in the asymmetric C₂ Cl₂ F₄ (i.e., CCl₂ FCF₃)isomer.

Suitable hydrochlorofluorocarbons for disproportionation include CH₂ClF, CH₃ CClF₂, and CHClFCF₃. The products of the disproportionationreactions are respectively, CH₂ F₂ and CH₂ Cl₂, CH₃ CF₃ and CH₂ ═CCl₂,and CHCl₂ CF₃ and CHF₂ CF₃.

Pressure is not critical. Atmospheric and superatmospheric pressures arethe most convenient and are therefore preferred.

The reaction products are separated by conventional techniques, such asdistillation. Some of the reaction products will have desired propertiesfor commercial use. For example CCl₃ CF₃ (CFC-113a) can be used toprepare CFC-114a which can then be converted to CH₂ FCF₃ (HFC-134a) byhydrodechlorination.

The process of this invention can be carried out readily in the vaporphase using well known chemical engineering practices.

The reaction zone and its associated feed lines, effluent lines andassociated units should be constructed of materials resistant tohydrogen fluoride and hydrogen chloride. Typical materials ofconstruction, well-known to the fluorination art, include stainlesssteels, in particular of the austenitic type, the well-known high nickelalloys, such as Mone1® nickel-copper alloys, Hastelloy® nickel-basedalloys and, Inconel® nickel-chromium alloys, and copper-clad steel.

Without further elaboration, it is believed that one skilled in the artcan, using the description herein, utilize the present invention to itsfullest extent. The following specific embodiments are, therefore, to beconstrued as merely illustrative, and do not constrain the remainder ofthe disclosure in any way whatsoever.

EXAMPLES Example 1

Preparation of Cubic Chromium Trifluoride

Commercial rhombohedral CrF₃ •4H₂ O (about 3 g) was placed in a goldcontainer and heated to 400° C. for 3-12 hours in air. The product wasrecovered and characterized. Powder x-ray diffraction measurements wererecorded at room temperature using a SCINTAG (PAD IV) commercialdiffractometer with copper k-alpha radiation, and indicated that thecrystal structure of the product formed can be indexed as cubic with alattice parameter of 10.201 Å (Table 2). The samples were weighed beforeand after the experiments. Weight loss measurements showed the compoundformed at 400° C./6 hours is CrF₃ (Table 1) as shown in the equation

    CrF.sub.3 •4H.sub.2 O→CrF.sub.3 +4H.sub.2 O.

(Weight loss observed: 39.8%, Weight loss calculated 39.77%). Theintensities of X-ray diffraction data show the compound has aface-centered cubic unit cell with space group Fd3m.

                  TABLE 1                                                         ______________________________________                                        Temp./time                                                                              Obs. weight loss                                                                          Phase formation                                         ______________________________________                                        200° C./12 hr                                                                    25.6%       Amorphous                                                 250° C./6 hr 28.4 Amorphous                                            300° C./6 hr 31.1% Amorphous + Cubic                                   350° C./12 hr 39.3% Cubic                                              400° C./3 hr 38.6% Cubic                                               400° C./6 hr 39.8% Cubic                                               400° C./12 hr 51.0% Amorphous + Cubic                                  500° C./3 hr 52.4% CrOF.sub.2 + Cr.sub.2 O.sub.3 + amor. +           ______________________________________                                                              Cubic                                               

                  TABLE 2                                                         ______________________________________                                        Powder X-ray diffraction Data for Cubic-CrF.sub.3                               (CrF.sub.3.4H.sub.2 O, 400° C./6 hours)                                d spacing (Å)                                                                           Relative Intensity                                                                        H       K   L                                     ______________________________________                                        5.8888      100         1         1   1                                         3.0674 46 3 1 1                                                               2.9423 33 2 2 2                                                               2.0818  7 4 2 2                                                               1.9547  4 5 1 1                                                               1.7991 14 4 4 0                                                             ______________________________________                                    

Catalyst Preparation for Use

Commercial CrF₃ •4H₂ O (about 54 g) was placed in a gold container andheated to 400° C. for 3 hours. The product was granulated to form 1.2 to1.7 mm particles for catalytic evaluation. The granulated product wassubsequently treated with anhydrous HF at 400° C. for 4 hours asdescribed below. The x-ray diffraction powder pattern of the product wasessentially the same as that given for cubic CrF₃ in Table 2.

General Procedure for HF Treatment of Cubic CrF₃

The granulated catalyst (9.2 g, 10 mL) was placed in a 5/8" (1.58 cm)Inconel® nickel alloy reactor heated in a fluidized sand bath. It washeated to 175° C. in a flow of nitrogen (50 cc/min) at which time HFflow (50 cc/min) was also started through the reactor. After 15 minutes,the nitrogen flow was decreased to 20 cc/min and the HF flow increasedto 80 cc/min. The reactor temperature was gradually increased to 400° C.during a 2 hour period and maintained at 400° C. for an additional 30minutes. At the end of this period the reactor was brought to thedesired operating temperature for catalyst evaluation under a nitrogenflow of 10 cc/min and an HF flow of 50 cc/min.

General Procedure for Product Analysis

The following general procedure is illustrative of the method used. Partof the total reactor effluent was sampled on-line for organic productanalysis using a Hewlett Packard HP 5890 gas chromatograph equipped witha 20' (6.1 m) long×1/8" (0.32 cm) diameter tubing containing Krytox®perfluorinated polyether on an inert carbon support. The helium flow was35 mL/min. Gas chromatographic conditions were 70° C. for an initialhold period of three minutes followed by temperature programming to 180°C. at a rate of 6° C./minute. Unless indicated, the reported results arein mole %.

The bulk of the reactor effluent containing organic products and alsoinorganic acids such as HCl and HF was treated with aqueous causticprior to disposal.

Legend

    ______________________________________                                        F115 is CClF.sub.2 CF.sub.3                                                                      F31 is CH.sub.2 ClF                                          F114a is CCl.sub.2 FCF.sub.3 F32 is CH.sub.2 F.sub.2                          F113 is CCl.sub.2 FCClF.sub.2 F113a is CCl.sub.3 CF.sub.3                     F123 is CHCl.sub.2 FCF.sub.3 F124 is CHClFCF.sub.3                            F124a is CHF.sub.2 CClF.sub.2 F125 is CHF.sub.2 CF.sub.3                      F134a is CH.sub.2 FCF.sub.3 F281ea is CH.sub.3 CHFCH.sub.3                    F227ea is CF.sub.3 CHFCF.sub.3 F1112a is CCl.sub.2 ═CF.sub.2                                F1123 is CHF═CF.sub.2 F1216 is CF.sub.3 CF═CF.                       sub.2                                                        HC1270 is CH.sub.3 CH═CH.sub.2 F1316 is C.sub.4 Cl.sub.2 F.sub.6        ______________________________________                                    

Example 2

Fluorination of Dichloromethane

    CH.sub.2 Cl.sub.2 →CH.sub.2 ClF+CH.sub.2 F.sub.2

The General Procedures for HF Treatment of Cubic CrF₃ and ProductAnalysis were used. The HF:dichloromethane molar ratio was 4:1 and thecontact time was 15 seconds. Results at various temperatures are shownin Table 3.

                  TABLE 3                                                         ______________________________________                                        TEMP. ° C.                                                                        F32          F31    CH.sub.2 Cl.sub.2                              ______________________________________                                        175        2.5          12.1   85.4                                             200 4.6 13.8 81.6                                                             225 40.7 13.0 46.2                                                            250 57.1 12.4 30.5                                                            275 57.4 13.1 29.4                                                          ______________________________________                                    

Example 3

Fluorination of F113a

    CCl.sub.3 CF.sub.3 +HF→CCl.sub.2 FCF.sub.3

The General Procedures for HF Treatment of Cubic CrF₃ and Product wereused. The organic feed composition to the reactor was 99.8% F113a and0.2% F114a. The HF:organic ratio was 2:1 and the contact time was 30seconds. Results at various temperatures are shown in Table 4.

                  TABLE 4                                                         ______________________________________                                        TEMP. ° C.                                                                     F115    F114a    F113a  F1112a OTHERS                                 ______________________________________                                        250     0.0     0.5      98.8   0.3    0.4                                      275 0.0 1.1 98.2 0.3 0.3                                                      300 0.0 4.1 95.3 0.3 0.4                                                      325 0.0 8.1 91.3 0.3 0.4                                                      350 0.6 86.8 12.4 0.0 0.1                                                   ______________________________________                                    

Comparative Example A

Fluorination of F113a

    CCl.sub.3 CF.sub.3 +HF→CCl.sub.2 FCF.sub.3

The General Procedures for HF Treatment of Cubic CrF₃ and ProductAnalysis were used. However, the catalyst that was used was rhombohedralchromium trifluoride (9.5 g, 10 mL, 12 to 20 mesh (1.68 to 0.84 mm)).The organic feed composition to the reactor was 99.7% F113a and 0.3%F114a. The HF:organic ratio was 2:1 and the contact time was 30 seconds.Results at various temperatures are shown in Table A.

                  TABLE A                                                         ______________________________________                                        TEMP. ° C.                                                                        F114a   F113      F1316 F113a                                      ______________________________________                                        230        0.1     0.1       1.0   98.5                                         275 0.3 0.2 0.5 98.9                                                          325 4.8 0.2 0.5 94.3                                                          350 24.9 0.1 0.3 74.0                                                         375 32.2 0.1 0.2 67.0                                                         400 60.8 0.1 0.2 38.3                                                       ______________________________________                                    

Example 4

Disproportionation of F124/F124a

    CHClFCF.sub.3 /CHF.sub.2 CClF.sub.2 →CHCl.sub.2 CF.sub.3 +CHF.sub.2 CF.sub.3

The General Procedures for HF Treatment of Cubic CrF₃ and ProductAnalysis were used. The organic feed composition to the reactor was98.5% F124 and 1.4% F124a. The contact time was 30 seconds except forthe last entry where it was 60 seconds. Results in mole % at varioustemperatures are shown in Table 5.

                  TABLE 5                                                         ______________________________________                                        Temp. (° C.)                                                                   %F125    %F124a   %F124  %F123  %Others.sup.a                         ______________________________________                                        250     0.1      1.4      98.1   0.2    0.2                                     275 0.9 1.4 96.6 1.0 0.2                                                      300 35.1 0.6 29.7 33.5 1.3                                                    325 39.4 0.5 23.2 34.5 2.6                                                    350 44.5 0.4 18.3 30.9 6.0                                                    350 46.7 0.4 17.2 28.2 8.3                                                  ______________________________________                                         .sup.a Others include CCl.sub.2 ═CCl.sub.2 and CCl.sub.2 ═CClF   

Example 5

Hydrofluorination of F1216

    CF.sub.3 CF═CF.sub.2 +HF→CF.sub.3 CHFCF.sub.3

The General Procedures for HF Treatment of Cubic CrF₃ and ProductAnalysis were used. The organic feed composition to the reactor was99.7% F1216. The HF:organic ratio was 3:1 and the contact time was 15seconds. Results at various temperatures are shown in Table 6. The first350° C. run was sampled at 3.5 hours on stream; the second was sampledat 10 hours.

                  TABLE 6                                                         ______________________________________                                        Temp. (° C.)                                                                     %F1216       %F227ea  %Others                                       ______________________________________                                        300       94.5         5.2      0.2                                             325 73.3 26.3 0.3                                                             350 12.2 87.2 0.5                                                             350 44.0 55.6 0.3                                                           ______________________________________                                    

Example 6

Hydrofluorination of HC1270

    CH.sub.3 CH═CH.sub.2 +HF→CH.sub.3 CHFCH.sub.3

The General Procedures for HF Treatment of Cubic CrF₃ were used. Howeverthe product analysis was done using a GC equipped with a 105 m×0.2 mm IDcapillary column coated with 100% dimethyl polysiloxane. All the linesto or from the reactor, i.e., inlet, outlet and valve box were at 50° C.The GC injection port was at 75° C. The organic feed composition to thereactor was 99.5% HC1270. The HF:organic ratio was 4:1 and the contacttime was 15 seconds. Results in area% at various temperatures are shownin Table 7.

                  TABLE 7                                                         ______________________________________                                        Temp. (° C.)                                                                     %HC1270      %F281ea  %Others                                       ______________________________________                                        125       29.3         69.8     0.9                                             100 27.7 72.1 0.2                                                              75 43.2 56.8 0.0                                                              50 53.4 46.6 0.0                                                           ______________________________________                                    

Example 7

Hydrofluorination of F1123

    CHF═CF.sub.2 +HF→CH.sub.2 FCF.sub.3

The General Procedures for HF Treatment of Cubic CrF₃ and ProductAnalysis were used. The organic feed composition to the reactor was98.9% F1123 and 0.8% F134a. The HF:organic ratio was 4:1 and the contacttime was 15 seconds. At 250° C., the products contained 19.5% F1123 and80.2% F134a.

We claim:
 1. A catalytic composition comprising chromium in the form ofcrystalline chromium fluoride having a cubic crystal structure andhaving the following X-ray diffraction powder pattern:

    ______________________________________                                        d spacing (Å)                                                                         Relative intensity                                                                        H        K   L                                        ______________________________________                                        5.8888      VS          1        1   1                                          3.0674                   S             3   1   1                              2.9423                   M             2   2   2                              2.0818                   W             4   2   2                              1.9547                   W             5   1   1                              1.7991                   M             4   4   0                            ______________________________________                                    


2. The catalytic composition of claim 1 wherein the catalyticcomposition further comprises other chromium compounds and at least 10percent of the chromium in the composition is in the form of said cubicchromium trifluoride.
 3. In a process for changing the fluorine contentof halogenated hydrocarbons containing from one to six carbon atoms, inthe presence of a chromium-containing catalyst, the improvementcomprising using the catalvtic composition of claim 1 as thechromium-containing catalyst.
 4. The process of claim 3 wherein asaturated or olefinic compound of the formula C_(n) H_(a) Cl_(b) F_(c),wherein n is an integer from 1 to 6, a is an integer from 0 to 12, b isan integer from 0 to 13 and c is an integer from 0 to 13, provided thatb is at least 1 when the compound is saturated, is reacted with HF inthe vapor phase in the presence of said catalyst to increase thefluorine content of said compound.
 5. The process of claim 3 wherein acompound having the formula C_(p) H_(g) F_(h) Cl, where p is an integerfrom 1 to 2, g is an integer from 1 to 3 and h is an integer from 1 to4, undergoes disproportionation in the presence of said catalyst.
 6. Thecatalytic composition of claim 2, wherein the catalytic compositionincludes said cubic chromium trifluoride in combination with at leastone material selected from the group consisting of magnesium fluorideand zinc fluoride.
 7. In a process for changing the fluoride content ofhalogenated hydrocarbons containing from one to six carbon atoms, in thepresence of a chromium-containing catalyst, the improvement comprisingusing the catalytic composition of claim 6 as the chromium-containingcatalyst.
 8. A catalytic composition consisting essentially of acrystalline chromium fluoride having a cubic crystal structure with alattice parameter of 10.201 Angstroms and having the following X-raydiffraction powder pattern:

    ______________________________________                                        d spacing (Å)                                                                         Relative intensity                                                                        H        K   L                                        ______________________________________                                        5.8888      VS          1        1   1                                          3.0674                   S             3   1   1                              2.9423                   M             2   2   2                              2.0818                   W             4   2   2                              1.9547                   W             5   1   1                              1.7991                   M             4   4   0                            ______________________________________                                    


9. In a process for changing the fluorine content of halogenatedhydrocarbons containing from one to six carbon atoms, in the presence ofa chromium-containing catalyst, the improvement comprising using thecatalytic composition of claim 8 as the chromium-containing catalyst.